Angle Conversion
Angles In Circles Tutorial for calculating angles in circles formed from radii, chords, tangents and secants.

Calculator for Constructing Regular Polygons

Draw a circle, measure the radius and this calculates the length of the polygon's sides.

Central Angle Calculator Calculates Central Angle of a Circle, Radius or Arc Length

Circle Circumference & Area

CIRCLE Sector, Segment, Chord, & Arc

Circle Equation Tutorial

Explains equations of the type x² + y² = r²

Circle Equation Calculator

Input 3 points and it calculates a circle's center radius and equation.

Ellipses

Types of Triangles
A chart showing triangles classified by angles
(acute, right, obtuse) and by sides (equilateral, isosceles, scalene).

Also has triangle area formulas and a triangle area calculator.

Triangle Centers
A tutorial discussing the incenter, circumcenter, centroid, orthocenter and the Euler line.

Triangle Tester
Calculates if 3 sides will form a triangle or not.

Right Triangles (Pythagorean Theorem)

30 60 90 and 45 45 90 Triangle Calculator

Regular Polygons

Quadrilateral page Descriptions and graphics discussing 6 different types of quadrilaterals.

Trapezoid Calculator

How to Calculate Trapezoid Area

Calculator for Parallelograms Squares Rectangles Rhombuses

Quadrilateral Kite Calculator